1. Field of the Invention
The present invention relates generally to a drying process for use in the production of a carboxylic acid. More specifically, the present invention concerns a method for drying solid particles of terephthalic acid in a drying zone where the residence time of the solid particles in the drying zone is reduced and the exit temperature of the solid particles is less than about 250° C.
2. Description of the Prior Art
In conventional crude terephthalic acid (CTA) production processes, para-xylene undergoes oxidation to form CTA particles. The CTA particles are then typically subjected to isolation and washing. In a conventional purified terephthalic acid (PTA) production process, an additional step is employed where the CTA particles are purified prior to the isolation/washing step. In either a CTA or a PTA production process, the terephthalic acid (TPA) particles exiting the isolation/washing step are typically in the form of a wet cake. In some TPA production processes, the wet cake is then dried in a dryer to thereby produce a substantially dry TPA product.
Various methods are known in the art for drying a TPA product. Such methods include the use of a rotary dryer, as well as drying the TPA wet cake by contacting it with a flow of inert gas, which can be achieved in a fluid bed dryer, a ring dryer, or in a solids conveying system. However, conventional methods for drying TPA can cause significant product degradation and/or sublimation, both of which are undesirable. Accordingly, there is a need for methods and/or equipment that can minimize product degradation and/or sublimation when drying a TPA product.